Method of producing dicalcium phosphate.



EUGEN BERGMANN, OF OHLAU, GERMANY.

METHOD OF PRODUCING DICALCIUM PHOSPHATE.

Specification of Letters Patent.

ramm d April 30, 1907.

Application filed October 13, 1903. Serial No. 176,873.

phate is dissolved in cold aqueous sulfurous acid and the sulfurous acidis then eliminated from such solution by boiling.

by boiling Precipitate. ZCaHPO 0250,, +380 +3H O.

(Compare llagners J ahresbericht 1882, page 389. Investigations byRotondi). The dicalcium phos hate obtained by such reactionhas theisadvantage that theprecipitate contains calcium sulfite, which appearsto render its suitability as an ingredient for cattle food doubtful, asno investi ations have been made on the action of sul ites on thestomachs of animals.

In order to obtain a dicalcium phosphate free from the sulfite ofcalcium, this invention provides that monocalcium phos hate should beadded to the solution of trica cium phosphate in aqueous sulfurous acidor to the precipitate obtained by boiling such solution, and then thesulfurous acid should be expelled by boiling:

The sulfurous acid must be expelled by boiling, as in the cold, thelatter would cause 'the reformation of monocalcium phosphate Thisprocess is distinguished from the known method of producing calciumphosphate from a solution of tricalcium phosphate in cold aqueoussulfurous acid by the fact that, as stated, a precipitate free fromcalcium sulfite results. The other known methods whereby dicalciumphosphate is precipitated by milk of lime, from a solution of phosphateof lime in hydrochloric acld (as in the maceration of bones) or from asolu tion of mineral phosphate in acids, are attended with thedisadvantage that the acids used as solvents are entirely lost and that,further, the use of milk of lime becomes necessary. In the presentinvention however the expense of lime as a means of precipitating, andof acids as solvents is done away with. By these means dicaloiumphosphate can be produced from a solution of tricalcium phosphate incold hydrated sulfurous acid or from the precipitate obtained from suchsolution by boiling, the distinctive feature whereof is that themonocalcium phosphate is added to the reaction mixture and the sulfurousacid is then eliminated by boiling.

Having now particularly described and ascertained the nature of myinvention and in what manner the same is performed, I declare that WhatI claim is:

1. The process of manufacturing dicalciu phosphate, which consists oftreating the product resulting from the solution of tricalcium phosphatein aqueous sulfurous acid with monocalcium phosphate, and applying heatto decompose the sulfite and expel sulfurous acid.

2. The process ofmanufacturing dicalcium phosphate, which consists ofboiling a solution of tricalcium phosphate in aqueous sulfurous' acidformin a precipitate containing calcium sulfite, a ding monocalciumphosphate to the precipitate and subsequently boiling this mixture forthe purpose of obtaining a precipitate free from calcium sulfite.

3. The process of producing dicalcium phosphate from tricalciumphosphate by treatin the latter with aqueous sulfurous acid and addingmonocalcium phos hate and causing re-action by heating, w ereby thesulfite is decomposed and sulfurous acid finally expelled.

In testimony whereof I have signed this specification in the presenceoftwo subscribing witnesses.

EUGEN. BERGMANN.

Witnesses WOLDEMAR HAUPT, HENRY HASPER.

